With the development of radio communication technology, people greatly improve the reverse receiving sensitivity of the base station through frequency expanding technology, diversity technology, smart antenna technology, and etc., and at the same time, higher power is needed to transmit the signals of the base station so as to balance the forward/reverse power of the system and reduce the cost of the system. In addition, frequency spectrum resource is increasingly becoming a rare resource, in order to improve the utilization efficiency of the frequency spectrum so as to carry more information in the unit bandwidth, the amplitude and phase of the signal are designed to carry information, and this renders sharp change of the amplitude of the signal, which is represented by the non-constant envelope characteristic and the peak-to-average power ratio of the signal. In order to interact more information, the bandwidth of the signal is becoming wider and wider. In practical application, the increase in the number of users renders the demand for the multi-carrier system more and more urgent, and in order to avoid the interference between the carriers and the interference of the present system to other systems, it is required that the radio frequency amplifier has high adjacent channel suppression ratio and low spurious emission, and hence, the linearization technology of the power amplifier becomes a key technology in modern radio communication system.
The linearization system of the power amplifier can be divided into two parts: one is a compensation system of the nonlinear distortion, and the other part is a self-adaptive adjusting system of the nonlinear distortion compensation parameter. The latter adjusts the compensation parameter of the power amplifier nonlinear distortion self-adaptively according to the distortion magnitude, thereby realizing that the linearization system of the power amplifier has better linear index in each application circumstance. The detection of the distortion magnitude is the basis of the self-adaptive adjustment of the compensation parameter, and the detection accuracy thereof directly determines the improvement of the performance of the whole linearization system, and therefore, the detection of the distortion magnitude is an important technology in the linearization technology of the power amplifier.
In the current method for extracting the distortion magnitude, it is necessary to demodulate the output signal, analyze and process the demodulated baseband signal, filter the useful signals through shifting frequencies and using better rectangle coefficient of the intermediate frequency filter, so as to obtain distortion. The prior art depends on the frequency and bandwidth of the input signal, and the original distortion is not obvious, which is unfavorable for the distortion detection.